Prostate Screening

Prostate cancer screening with the prostate specific antigen (PSA) test and digital rectal examination (DRE) have resulted in an increase in prostate cancer detection. In addition, cancers are now being detected at earlier stages when they are potentially curable. Before screening, most prostate cancers were detected only when they produced local symptoms or had spread, a point where a cure is often impossible.

The Digital Rectal Exam (DRE)
The most basic test for detecting prostate cancer is the digital rectal DRE. During the DRE, the urologist inserts a gloved forefinger into the rectum to detect enlargement or other abnormalities of the prostate. Although the DRE is not a definitive test for cancer, regular exams help the urologist detect changes the prostate might undergo over time. If the DRE is felt to be abnormal, then a prostate biopsy should be performed because an abnormal DRE is associated with a fivefold increased risk of cancer at the time of screening.

The Prostate-Specific Antigen (PSA) Test
The PSA test has revolutionized screening for prostate cancer. Prostate-specific antigen is a substance produced by the prostate gland and released into the blood. The test measures the amount of PSA in the blood, which is expressed in nanograms per milliliter (ng/mL). The level of PSA in serum can be increased by inflammation of the prostate, urinary retention, prostatic infection, benign prostatic hyperplasia, prostate cancer and prostate manipulation. Although PSA has good sensitivity, it is not an ideal test because an elevated PSA is neither specific to prostate cancer nor does it distinguish aggressive prostate cancers from those that are biologically benign. The following PSA levels are used to assess the risk of cancer.

If your level is above 4 but below 10, you have about a 15 percent to 25 percent chance of having prostate cancer. If your PSA is greater than 10, your chances of having prostate cancer are higher. However, the threshold of 4ng/mL for the purposes of detection may not accurately indicate the presence of disease. In the Prostate Cancer Prevention Trial (PCPT), 15% ofthe men with a PSA < 4 with a normal DRE were found to have prostate cancer. The clinical significance of these cancers remains to be determined. Therefore, many urologists now use an age-adjusted PSA range to aid in screening as follows:

Despite its limitations, the PSA test has helped detect cancer in countless men. In 1984, before PSA testing was available, the chance of finding localized prostate cancer was about 50%, either incidentally or during other procedures. In 1993, after PSA testing became widely used, that figure jumped to over 90%. New literature has also emphasized the importance of PSA testing in identifying aggressive cancers by observing the change in PSA over time.

Recommendations
The American Cancer Society (ACS) and American Urological Association (AUA) recommends that the PSA test and DRE should be part of a man?s annual physical exam beginning at age 50 for men with a life expectancy of at least ten years. In high-risk men (African Americans and those with a first degree relative with prostate cancer), screening should be offered at an earlier age 40.

Before testing, patients should discuss with their physicians the potential benefits of early prostate cancer detection and the possible need for subsequent treatment. In doing so, the patients can make an informed decision about undergoing screening.

There are two major ongoing trials for prostate cancer screening: The Prostate, Lung, Colorectal and Ovarian (PLCO) trial in the United States and the European Organization for Research and Treatment of Cancer (EORTC) trial. The PLCO trial is expected to finalize screening in 2007 with long-term data reported following 10 years of follow-up.

Noteworthy recent literature regarding Preventian
The Prostate Cancer Prevention Trial (PCPT) described the prevalence of histologically proven prostate cancer among men randomized to receive daily finasteride therapy to decrease the prostate size versus a placebo. The authors described a 24.8 percent reduction in the prevalence of prostate cancer. However, the cancers that developed in the treatment arm were a higher grade.